c,function,serial-port,posix , Counting bytes received by posix read()


Counting bytes received by posix read()

Question:

Tag: c,function,serial-port,posix

I get confused with one line of code:

temp_uart_count = read(VCOM, temp_uart_data, 4096); 

I found more about read function at http://linux.die.net/man/3/read, but if everything is okay it returns 0, so how we can get num of bytes received from that?

temp_uart_count is used to count how much bytes we received from virtual COM port and stored it to temp_uart_data which is 4096 bytes wide.

Am I really getting how much bytes i received with this line of code?


Answer:

Yes, temp_uart_count will contain the actual number of bytes read, and obviously that number will be smaller or equal to the number of elements of temp_uart_data. If you get 0, it means that the end of file (or an equivalent condition) has been reached and there is nothing else to read.

If it returns -1 this indicate that an error has occurred and you'll need to check the errno variable to understand what happened.


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